Historically, the ALOHA protocol is the first distributed random access channel access protocol based on a single-hop access network using packet switching on a radio channel. The channel access control is better known by the abbreviation “MAC”, or Medium Access Control. The ALOHA protocol enables each user to transmit data when he or she wishes. If the sender receives a confirmation by the recipient of the correct reception of a packet within a certain period of time, then he or she knows that no conflict has occurred. Otherwise, at the end of this period of time, he or she assumes that a collision has occurred and that the packet must be retransmitted. In order to avoid the continual repetition of the access conflicts, the retransmission time period is random, thus avoiding having users transmit or retransmit at the same instants. A synchronous version of ALOHA is obtained by dividing the time into intervals of durations equal to the duration of transmission of a packet. When two packets are in collision, then they overlap completely rather than partially, leading to an increase in the use of the channel to 36% instead of 18% for the asynchronous ALOHA. The main improvement in the design of the random MAC protocols has been the introduction of the carrier sense multiple access (CSMA) technique. The CSMA protocol reduces the level of interferences provoked by the packet collisions by enabling each terminal to listen beforehand to a channel and detect any transmissions in progress. The MAC protocol of the popular IEEE802.11 standard is widely used for wireless local area networks, FIG. 1A. It employs a multiple access scheme based on listening to the channel and a retransmission mechanism with binary exponential windows. In single-hop networks in which all the nodes mutually see each other, the protocols based on the CSMA protocol achieve a very good use of the transmission or communication channel of the order of 80% [1][2].
The absence of direct visibility between all the nodes of the network has a negative impact on the access protocols based on listening to the channel because of the problem of the hidden terminal illustrated in FIG. 1B where a user A can communicate with a user B within radio or visibility range but cannot communicate with a user C. In order to solve this problem of the hidden terminal, the IEEE 802.11 protocol, FIG. 1C, has defined a second access mechanism which performs a reservation of the channel in the neighbourhoods of the sender and of the receiver. The reservation is obtained by the exchange of two signalling messages, a first request to transmit message, known by the abbreviation RTS (Request To Send) and a second “ready to send” message, better known by the abbreviation CTS (Clear To Send), which block access to the channel for the terminals which receive them. The RTS/CTS mechanism aims to achieve a re-use of the channel with two radio hops. However, the mechanism does not manage to correctly solve the problem of the hidden terminal because its correct operation requires the nodes of the network to have access to all the reservation messages for their neighbourhoods. This constraint is impossible to observe in multiple-hop networks because of the problem of the masked terminal. The problem of the masked terminal therefore greatly degrades the performance levels of the protocol in the multiple-hop networks and this problem is exacerbated when the size of the network increases because the number of hidden/masked terminals also increases. FIG. 1C illustrates the problem of the masked terminal, C.
To the knowledge of the applicant, no protocol in the literature defines a mechanism that can support a maximum re-use of the channel, thus making it possible to achieve the maximum transmission capacity of the channel and achieve the theoretical maximum capacity of an ad hoc network in the model of the channel with collision. This is because, in an optimal access mechanism, only the neighbours of the receivers can access the channel.